Radial pump with static eccentric and rotatable cylinders

ABSTRACT

A pump for conveying a medium, especially a gas-liquid mixture, with a housing, an annular surface extending inside the housing, an eccentric arranged off center in relation to the annular surface and at least one displacer arranged between the annular surface and the eccentric. The displacer is held in position in relation to the annular surface and the annular surface can rotate in relation to the eccentric. A hollow shaft delivers mixture to the eccentric which has connections to the displacer for delivering mixture to and receiving it from the displacer.

BACKGROUND OF THE INVENTION

The present invention relates to a pump for conveying a medium, inparticular a gas-liquid mixture, and particularly to the structure ofthe eccentric controlled pumping elements.

From the state of the art many different types of pumps are known.Radial piston pumps, for example, have a cylinder block that liesoff-center inside a housing. In the cylinder block, pistons are arrangedradially which, during the turning of the cylinder block, execute astroke movement. Normally the pistons are supported in the housing byrollers.

Such radial piston pumps have the disadvantage that their construction,in particular the guiding of the pistons in the cylinder block isrelatively complicated. In addition, such pumps pose problems whenconveying gas-liquid mixtures which occur, in particular, when conveyingcrude oil. To avoid these problems the natural gas present in the crudeoil is first separated by compensators and after the pump it is fed inagain via compressors. However, this process is very complicated andexpensive.

SUMMARY OF THE INVENTION

The object of the present invention is, therefore, to provide a pumpwhich has a simple construction and can be used to convey gas-liquidmixtures.

This object is achieved by providing a pump having an enclosed housingwith an annular, inwardly facing surface inside and extending around thehousing, a generally tubular eccentric extending inside and axiallythrough the annular surface and disposed eccentric to the axis of theannular surface; a displacer adapted for radial displacement disposedbetween the annular surface and the eccentric and rotatable around theaxis of the annular surface. There is a supply of a liquid gas mixtureto be pumped and an outlet from the pump. The displacer selectivelydraws the mixture from the supply into the displacer and/or pump themixture from the displacer as the radial space between the eccentric andthe annular surface correspondingly changes in size. The annular surfacemay be connected with a shaft, particularly a hollow shaft, whichrotates the annular surface and the shaft may, in turn, be rotated by amotor rotor or even may be part of the motor. The supply of liquid isthrough the eccentric. The eccentric has respective inlet and outletchambers which respectively communicate with the displacer at differentlocations around the annular surface for receiving liquid mixture fromthe supply or for pumping it and out of the pump. Sealing arrangementsfor the displacers and various numbers of displacers are also disclosed.With the solution according to the invention so-called displacers areused, which each have a changeable volume displacer chamber. Thedisplacers are arranged between an annular surface located radiallyinward and an eccentric arranged eccentrically to and radially outwardof the annular surface. The annular surface, in addition to supportingthe displacers, serves to hold the displacers in a fixed position oni.e. non-rotatable with respect to the annular surface, so that they canturn relative to the eccentric. During the turning, because of theeccentricity, the radial distance between the annular surface andeccentric, and accordingly also the volume of the displacer chambers,changes continuously.

With this arrangement it is possible to dispense completely with acylinder block as the displacers are individual, independent parts whichcan be installed in a simple manner between the eccentric and annularsurface. Furthermore, this design permits a compact and extremelyspace-saving construction.

According to an advantageous further development of the invention theannular surface is driven by a hollow shaft which, in addition, acts asmedium supply. As a result thereof the supplied medium is also made toturn. The centrifugal force acting on the medium causes the specificlighter gas to collect in a middle section and the specific heavierliquid medium in an outer ring-shaped area. With the aid of thisseparation an optimal charging of the displacer chambers takes placeand, accordingly, an extremely good conveying of such gas-liquidmixtures.

It is also advantageous to carry out the medium supply decentred, i.e.not via the drive shaft for the annular surface. Preferably, the mediumis passed through an annular casing section which extends in thelongitudinal direction of the housing and adjoins the stator of the pumpmotor. This has the advantage that the conveying capacity is increasedand at the same time a cooling of the motor can be ensured by means ofthe conveyed medium. Furthermore, this decentred supply results in anadditional soundproofing obtained by the screening effect of the annularcasing section.

Naturally, the central medium supply via the hollow shaft can also becombined with the decentred supply.

According to a further advantageous embodiment of the invention thedisplacer is constructed in such a way that it is in friction contactwith the annular surface. This makes it possible to hold the displaceragainst the annular surface without using additional holding means.

In an advantageous embodiment the displacer consists of a first movabledisplacer element resting against the eccentric and a second displacerelement or piston resting against the annular surface, wherein the firstdisplacer element can be moved radially to the annular surface. As aresult of this telescope-like shifting of the two displacer elementsrelative to one another, the displacer volume is alternatingly increasedand reduced during every rotation around the eccentric. The constructionof such a displacer is very simple, so that it can be produced at areasonable cost.

In another advantageous further development the displacer has a sealingelement, which rests sealingly against the eccentric, wherein preferablya concave sealing shoe adapted to the outside surface of the eccentricis used. Also here an effective seal is produced between the displacerchamber and eccentric by very simple means and, accordingly, also at lowcost. Preferably, the first and the second displacer elements arespring-loaded, so that the first displacer element is pressed againstthe eccentric and the second displacer element against the annularsurface with a defined force.

In a further advantageous embodiment of the invention, a valve ring isprovided between eccentric and displacer, in which case the displacersrest against the valve ring in a fixed position and the valve ring canrotate around the eccentric. As a result thereof the medium supply anddischarge can be fashioned more freely without the need of being subjectto an annular peripheral surface. All that needs to be ensured is thatthe valve ring is adequately supported.

In a further development the first displacer element is held against thevalve ring in the radial direction, wherein preferably on at least twooutside surfaces of the first displacer element grooves are provided,into which the lugs formed onto the valve ring can engage. With the aidof this design the installation can be simplified further and thecentrifugal force acting on the second displacer element can be utilisedto ensure that it is held properly against the annular surface withoutrequiring an additional spring.

Preferably, several such valve rings are used which in the axialdirection are arranged above one another and which preferably havedifferent eccentricities. With this the conveying capacity can beincreased in a very simple manner.

Preferably, the eccentric has an axial opening which adjoins an openingof the hollow shaft in such a way that the medium can flow into theeccentric. The peripheral surface of the eccentric is preferablyprovided with an outlet opening and an inlet opening, which normally lieopposite one another. The outlet opening is connected to the axialmedium supply and the inlet opening to an also axial medium discharge.In this way a very simple medium supply can be realised.

Preferably, the medium supply as well as the medium discharge each havea non-return valve, so that the pump is also suitable for very highpressures.

In a further embodiment of the invention the hollow shaft is constructedas the rotor shaft of an electric motor, so that the medium to beconveyed flows axially through the motor. This construction is extremelycompact and space-saving, and because of the axial throughflow of themedium the pump can be used directly in a pipe line.

Further advantageous embodiments can be noted from the sub-claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in greater detail withreference to exemplified embodiments illustrated in the drawings,wherein:

FIG. 1 shows a diagrammatic longitudinal section through a pumpaccording to a first exemplified embodiment;

FIG. 2 shows a diagrammatic longitudinal section through a pump of asecond exemplified embodiment;

FIG. 3 is a longitudinal section through the pump of a third exemplifiedembodiment,

FIG. 4 is a diagrammatic view of several displacers;

FIGS. 5a and b show another exemplified embodiment of a displacer,

FIG. 6 is a longitudinal section through the pump of a fourthexemplified embodiment, and

FIG. 7 is a diagrammatic longitudinal section through the pump of afifth exemplified embodiment.

FIG. 1 illustrates diagrammatically in longitudinal section a pump 1,wherein the parts that are not essential to the invention have been leftout. The pump 1 consists of a long housing 3, the one longitudinal endof which is closed off by a removable cover 7. The other longitudinalend 9 of the housing 3 has a shaft opening 11 as well as a cup-shapedinlet filter 5 mounted onto the outside.

A shaft 13, which passes through the shaft opening 11, extends insidethe housing 3 in the longitudinal direction, wherein inside the housingnear the cover 7 the shaft 13 ends in a beaker-shaped section 15, theopen side of which faces the cover 7. This beaker-shaped section 15consists of an annular surface 17 which lies concentrically to thelongitudinal axis of the shaft 13, and a radial surface 19 extendingradially from the shaft 13 to the annular surface 17. The outsidediameter of the beaker-shaped section 15 is, therefore, greater than theoutside diameter of the shaft 13.

The shaft 13 itself is a hollow shaft with an opening 21 at each of itsaxial ends. This, therefore, provides a communication between theopening 21 of the shaft 13 facing the end face 9 and the space 23enclosed by the annular surface 17.

The shaft 13 with its beaker-shaped section 15 is supported rotatably bybearings 25 arranged in the housing 3, which bearings for the sake ofclarity have been shown in only one spot in the Figure. The otherbearing required for a secure support preferably is positioned close tothe beaker-shaped section 15.

The only shaft opening 11 in the housing 3 is provided with a sealingelement 27, preferably an O-ring.

Inside the housing 3 an electric motor is provided which is indicatedpurely diagrammatically by the two rectangles 29, i.e. in the form of ablack-box. This black-box 29 contains, for example, the stator windings,the electric supply lines as well as, for example, sliding contacts. Thearrangement and construction of such an electric motor, preferably adirect-current motor, is known to the expert and therefore no furtherdetails will be given here. All that needs to be mentioned is that anarmature winding 31 of the motor 29 forms part of the hollow shaft 13.The hollow shaft 13, therefore, not only acts as medium supply but alsoas a drive shaft.

The cover 7 connected to the housing 3 has a bore 33 which passescompletely through the cover 7. The section 35 of the bore 33 pointingto the outside has a screw-thread 37 so that, for example, a notillustrated connection piece can be screwed in. An eccentric 39 isfastened with its flange-like end 41 to the inside of the cover 7, e.g.by screws. To ensure a scaling, O-rings can, for example, be usedhere--not illustrated in the drawing.

In the present exemplified embodiment the eccentric 39 is circular,wherein its longitudinal axis does not coincide with the longitudinalaxis of the hollow shaft 13 and of the beaker-shaped section 15. Thelongitudinal axis 43 of the eccentric 39 is offset relative to thelongitudinal axis 44 of the hollow shaft 13 by an amount v.

Because of this eccentric arrangement the distance--seen in theperipheral direction--between the outside peripheral surface 45 of theeccentric 39 and the inside annular surface 47 changes continuously.

The end of the eccentric 39 positioned opposite the flange 41 lies veryclose against the radial surface 19, the opening 21 of the hollow shaft13 being covered completely. In this end of the eccentric 39 an axialbore, preferably a blind hole 48, is provided which co-operates with theopening 21.

By means of a radial bore 49' in the peripheral surface 45 of theeccentric 39 a further communication is created between the axial bore48 to the outside.

At the opposite end of the eccentric another axial bore 51 is provided,which co-operates with the inside opening of the bore 33 in the cover 7.The peripheral surface 45 of the eccentric 39 is again provided with afurther bore 49", which creates a communication between the axial bore51 and the annular space 23.

Between the axial bore 48 and the axial bore 51 lies a wall section 53which ensures a separation of these bores.

In the present exemplified embodiment the radial bore 49' acts as outletopening and the radial bore 49" as inlet opening. Because the flowpasses through these openings from one side only, an optimal flowfavorable shape can be chosen.

Between the inside annular surface 47 and the outside peripheral surface45 of the eccentric 39, displacers 55 are arranged, two of whichdisplacers are shown in FIG. 1. Preferably, however, three or moredisplacers are used, the number of displacers influencing the uniformityof the conveying.

In the following such a displacer 55 will be described in greater detailwith reference to FIG. 4.

The displacer 55 with a preferably circular cross-section consists of afirst displacer element 57 and a second displacer element or piston 59.The first displacer element 57 is provided at its end facing theeccentric with a sealing shoe 61, the outline of which is adapted tothat of the outside peripheral surface 45 of the eccentric 39, so that atight seal is ensured.

The second displacer element 59 is positioned movably on the end of thefirst displacer element 57 opposite to the one with the sealing shoe 61,a displacer chamber 63 being formed between the first and seconddisplacer elements.

Inside the first displacer element 57 there extends a duct 65 whichbegins at the sealing shoe 61 and opens out in the displacer chamber 63.

Inside this displacer chamber 63 a spring 67 is arranged, which in turnrests on an inside wall of the second displacer element 59 and anopposite wall section of the first displacer element 57. This spring 67ensures that the second displacer element 59 is pressed against theannular surface 17 with a force determined by the spring.

This end 69 of the second displacer element 59 adjoining the annularsurface 17 is arc-shaped or cup-shaped, its radius being smaller thanthat of the annular surface 17. At the highest point of this cup-shapedend 69 a point-shaped lug 21 is provided, which alone is in contact withthe annular surface 17.

However, also other shapes of the end 69 adapted to the annular surface17 are possible.

The sealing off of the dispenser chamber 63 from the annular space 23takes place by a sealing ring 73 which is located in the peripheralsurface of the first displacer element 57 and rests against the insidewall surface 74 of the second displacer element 59.

From FIG. 1 it can be noted that the opening of the duct 65 facing theeccentric 39 (see FIG. 4) co-operates with the openings 49' and 49"respectively, so that the medium flowing into the axial bore 48 can flowthrough the bore 49' into the displacer chamber 63 of the bottomdisplacer 55, and the medium in the displacer chamber 63 of the topdisplacer 55 can flow through the bore 49" and the bore 33 to theoutside.

In the following the mode of functioning of the pump illustrated in FIG.1 will be explained.

The electric motor 29 drives the hollow shaft 13 and accordingly alsothe annular surface 17. This annular surface 17 holds the displacers 55and accordingly moves them along, so that they also move along acircular path. A suitable possibility for taking the displacers 55 alongconsists in providing friction contact between the annular surface 17and the end of the second displacer element 69, preferably thepoint-shaped lug 71. It must be ensured here that the static frictionforce occurring on the annular surface 17 is greater than that betweenthe sealing shoe 61 and eccentric surface 45. Otherwise the annularsurface will slip over the displacer so that it does not experience anymovement in relation to the eccentric.

Naturally, also other possibilities for taking the displacers along areconceivable, for example by stops provided on the inside annular surface47.

By the annular surface 17, which in accordance with the foregoing actsas a drive, the displacers 55 are turned around the eccentric, the firstdisplacer element 57 turning around the eccentric axis 45 and the seconddisplacer element 59 around the longitudinal axis 44 of the hollowshaft. Because of the eccentricity of the two axes 44, 45, during arotation the two displacer elements 57, 59 are pushed into one anotherin a telescope-like manner against the force of the spring 67, as aresult of which the space-volume of the displacer chamber 63 changes.

FIG. 4 shows, by way of example, two positions I and II, the displacerchamber 63 having the smallest space-volume in position I and thelargest space-volume in position II.

When the displacers 55 in this Figure are moved along in a clockwisedirection, the space-volume of the displacer chamber 63 will increasecontinuously from position I up to position II, to then again decreasecontinuously back to position I. The movement time from position I toposition II is referred to as the suction phase and the movement timefrom position II to position I as the expelling phase.

Getting back to FIG. 1, the medium to be conveyed, e.g. a mixture ofnatural gas and crude oil, flows through the filter 5 through theopening 21 into the hollow shaft 13. Because of the turning of thehollow shaft 13, the conveyed mixture also starts to turn when, due tothe centrifugal force, the heavier crude oil flows through an outersection of the hollow shaft 13, whereas the lighter natural gas isconveyed through in a middle section of the hollow shaft 13.

This flow at the end of the hollow shaft 13 now flows through theopening 21 into the bore 48. Next, the heavier liquid first flowsthrough the bore 49' into the displacer chamber 63. Because of thesuction effect of the increasing space-volume during the suction phase,this flowing-in is helped along or realised.

As soon as the displacer element 55 has reached the end of the suctionphase, i.e. position II, the connection to the bore 48 and accordinglyto the suction side of the pump is interrupted.

Shortly afterwards, during the expelling phase, the displacer element 55comes into the operating range of the opening 49", as a result of whicha connection is created to the outside side of the pump (here the bore33). Because of the reducing space-volume of the displacer chamber 63during the expelling phase, the medium present in this chamber isexpelled.

The turning of the hollow shaft 13 ensures that during every suctionphase liquid gets into the displacer chamber 63 of a displacer 55, sothat the pump will never run dry.

As in the exemplified embodiment illustrated in FIG. 1 no non-returnvalve is provided in the axial bore 51 which serves as outlet, it mustbe ensured that a displacer element 55 co-operates continually with theopening 49" or seals same off, respectively. A suitable possibilityconsists, for example, in designing the sealing shoes 61 of thedisplacer elements in such a way that together they engage around theentire periphery of the eccentric 39. If, therefore, for example threedisplacer elements are used, their sealing shoes 61 will each cover aperipheral area of 120°.

It is also possible, of course, to use more than three displacers 55, inwhich case in each instance also several bores 49' and 49" can beprovided.

Another possibility to ensure a sealing of the bores 49 and a connectionto the displacer elements 55, respectively, consists in using a valvering 75, as indicated diagrammatically in FIG. 4. This valve ring 75completely surrounds the eccentric 39 in its axial section where thebores 49 are provided. Bores 77 provided in the valve ring create aconnection from the inside of the eccentric to the outside into thedisplacers 55.

With this exemplified embodiment the sealing shoes 61 no longer slideover the peripheral surface of the eccentric, but are arrangedessentially in a fixed position in relation to the valve ring. Thefixing into position of the sealing shoes 61 on the valve ring 75 duringthe rotating can again be ensured by, for example, friction contact orstops, in which case the annular surface 17 drives not only thedisplacers 55 but also the valve ring 75.

The sealing of the bores 49 between two adjacent displacers 55 takesplace in this case not by the sealing shoes 61 but by means of sealingsections 79 in the valve ring. For the rest the mode of functioning ofthis arrangement corresponds to that already described with reference toFIG. 1, so that a further explanation can be dispensed with.

The other exemplified embodiment illustrated in FIG. 2 differs from theone shown in FIG. 1 among others in that non-return valves 81 areprovided in the eccentric 39. The non-return valves 81a and 81b arrangedon the suction side prevent the medium expelled from the displacerchamber 63 from flowing back again into the hollow shaft 13, but ensurethat via the non-return valves 81c and 81d which act opposite to thenon-return valves 81a and 81b it can flow to the bore 33. The bores 49are used as outlet as well as inlet openings, in contrast to theopenings 49 of FIG. 1 through which the medium flows from only one side.

Another difference compared to the pump illustrated in FIG. 1 is thatthe annular surface 17 is arranged in a fixed position in relation tothe housing 3. The eccentric 39, on the other hand, rotates around thelongitudinal axis of the hollow shaft 13. This is achieved in that theeccentric is constructed as an eccentric section of the hollow shaft 13,the end of which on the side of the cover being mounted centrally in abore of the cover 7. The rotationally tight sealing off to the outsidetakes place, for example, by an O-ring 83.

To obtain a change in the space-volume of the displacer chamber 63, theeccentric section 39 must execute a relative movement in relation to thedisplacer 55, so that as a result of the eccentricity a continuouschange in the distance between annular surface and peripheral surface ofthe eccentric takes place. As a result, also here the sealing shoe 61slides over the peripheral surface of the eccentric, as has already beendescribed in connection with the FIGS. 1 and 4.

For the rest the mode of functioning of this pump corresponds to the onealready described in connection with the exemplified embodiment ofFIG. 1. For this reason another explanation is dispensed with.

FIG. 3 illustrates another embodiment of the pump shown in FIG. 1.

This exemplified embodiment essentially corresponds to the one shown inFIG. 1, for which reason another description of the parts that bear thesame reference numerals will be dispensed with.

The only difference is that the displacer elements are arranged in twoparallel planes that are offset in the longitudinal direction of thehollow shaft 13. Each of these planes has an eccentric section 85a and85b, respectively, which form part of the eccentric 39 but havedifferent eccentricities in relation to the longitudinal axis 44.

Furthermore, no axial bore corresponding to the bore 48 is provided inthe eccentric 39. The medium supply takes place through inlet pockets 87which create a connection between the displacer chamber 63 and theannular space 23 filled with the medium. The sealing off of this annularspace 23 from the inside of the housing takes place by a ring 89 restingradially against the annular surface 17, which ring 89 is supported in asliding member on an area 91 of the cover 7 arranged concentrically tothe longitudinal axis 44.

As already explained with reference to FIG. 1, also in this case it mustbe ensured that the radial bores 49 that are in communication with thebore 33 do not come in contact with the annular space 23. This caneither be done by a suitable shaping of the sealing shoes or by the useof valve rings for every eccentric section, or by installing anon-return valve in the bore 33 or in the down-stream pressure line,respectively.

For the rest the mode of functioning corresponds to the one alreadydescribed.

FIG. 5 shows a further possibility for the construction of a displacerelement 55. This one also consists of a first displacer element 57 and asecond displacer element 59. However, in this case the second displacerelement 59 engages into the first displacer element 57.

In contrast to the displacer 55 shown in FIG. 4, this exemplifiedembodiment does not have a spring 67. Here the centrifugal force of therotating displacer 55 directed towards the annular surface 10 is used topress the second displacer element 59 against the annular surface 10. Toprevent that the first displacer element 57 is also moved towards theannular surface 17 by the centrifugal force, a forced guidance acting inthe radial direction is provided between this first displacer element 57and the valve ring 75. The forced guidance 93 is designed in such a waythat a suitable lug 97 of the valve ring 75 engages into grooves 95provided on at least two peripheral sides of the first displacer element57.

In the section along the line b--b in FIG. 5a, which is shown in FIG.5b, the entire valve ring 75 is shown. From this it can be seen that ithas flat surfaces 99 above which side walls 101 project on two oppositesides, which in turn have lugs 97. However, as a result of the alreadydescribed forced guidance of the displacer element 55, a shiftingparallel to the side wall 101 is possible, as indicated by the doublearrow in FIG. 5b.

For the rest mode of functioning of this valve ring corresponds to thatof the valve ring already described with reference to FIG. 4.

FIG. 6 shows another embodiment of the pump illustrated in FIG. 1.

As this exemplified embodiment essentially corresponds to the one shownin FIG. 3, another description of the parts bearing the same referencenumerals is dispensed with.

With the pump shown in FIG. 6 the only difference is that the mediumsupply does not take place centrally via the drive shaft 13, butdecentred via an annular casing section 110.

This annular casing section 110 extends from the end face 9 of the pumphousing up to the annular surface 17, passing directly along the statorof the pump motor. A bore 21 is provided in the end face 9 of thehousing through which the medium to be conveyed can enter the annularsection 110. Naturally, also several such bores 21 may be provided.

At the opposite end of the annular section 110, a radially inwardsextending connection 112 is formed through the annular surface 17 intothe space 23. The connection 112 may be provided in the form of bores oropenings distributed over the periphery of the annular surface 17.Naturally the filling of the space 23 with the medium to be conveyed canalso take place axially in the area of the ring 89.

Therefore, compared to the pump shown in FIG. 3, the medium is fed innot centrally via a hollow shaft 21, but decentred via the annularsection 110 into the space 23. However, the actual mode of functioningof the conveying does not change as a result thereof.

FIG. 7 shows another exemplified embodiment of a pump, which essentiallycorresponds to the one illustrated in FIG. 2. Also here the annularsurface 17 is arranged in a fixed position, whilst the eccentric 39turns and ensures the stroke movement of the displacer 55.

The only difference is that the medium supply is different. The mediumflows, as before, through the hollow shaft 13, but then--as indicated byan arrow--is deflected radially outwards into an inlet area 131. Fromthere it flows into the displacer chamber 63, passing beforehand throughan only diagrammatically indicated non-return valve 133. During theexpelling of the medium from the displacer chamber 63 an also onlydiagrammatically indicated non-return valve 135 opens, so that a flowpath is opened into an outlet area 137.

FIG. 7 clearly shows that the medium supply takes place parallel to thehollow shaft and transversely to the longitudinal axis of the displacer55 at least between the inlet area 131 and the outlet area 137.

From the outlet area 137 the medium flows preferably radially inwardsand then through a central bore 139 to the outside.

The pumps mentioned in the foregoing can be used in many ways. They can,for example, be used as borehole pump because of their good propertiesregarding the conveying of gas-liquid mixtures, However, the mentionedexemplified embodiments can also be used as circulating pumps in heatingsystems or as injection pumps in the medical field. These pumps can evenbe used for high pressure applications, in which case, for reasons ofsafety, non-return valves must, however, be provided in the inlet andoutlet ducts.

However, at very high pressures a slot control without valves, asillustrated for example in FIG. 1 or 3, is preferred.

It must be mentioned once again here that by reversing the medium flows,the described pumps can also be used as motors.

For the rest individual features of the mentioned exemplifiedembodiments may be combined in any way.

I claim:
 1. A pump for conveying a liquid with mixed gas, the pumpcomprisinga hollow external housing; a rotatable annular, inwardlyfacing drive surface extending around and inside the housing; agenerally static and tubular eccentric extending inside and axiallythrough the annular surface and disposed eccentric to the axis of theannular surface; a displacer adapted for radial displacement anddisposed between the rotatable annular surface and the static eccentric,the displacer being rotatable relative to the eccentric and beingrotated by the rotatable annular, inwardly facing drive surface aroundthe axis of the annular surface; the displacer is rotatively fixedrelative to and rotates along with the annular surface, the displacer isrotatable with respect to the eccentric, and the annular surface isrotatable around and relative to the eccentric; a supply of liquid gasmixture to the pump, an outlet for pumped mixture from the pump; thesupply of the mixture comprises a hollow shaft which is located in thehousing for delivering the mixture to the displacer, and the shaft isrotatable and is connected with the annular surface for rotatingtogether with the annular surface; the eccentric includes an axialopening communicating with the hollow shaft for receiving mixtureflowing axially into the eccentric from the hollow shaft, and the axialopening of the eccentric communicating with the displacer for supplyingmixture to the displacer; the displacer communicating with at least oneof the supply and the outlet for the mixture, for selectively drawingthe mixture from the supply into the displacer as the radial spacebetween the eccentric and the annular surface increases and for pumpingthe mixture from the displacer through the outlet as the radial spacebetween the eccentric and the annular surface decreases.
 2. The pump ofclaim 1, wherein the displacer is in friction contact with the annularsurface to be in a fixed position with respect to the annular surface.3. The pump of claim 1, wherein the eccentric has a peripheralsurface;an outlet opening through the peripheral surface from the axialopening in the eccentric and communicating to the displacer; an inletopening through the peripheral surface and into the axial opening of theeccentric; and means in the axial opening for separating the inlet andthe outlet openings to the eccentric; another opening from the housinglocated downstream from the inlet opening; the displacer beingconstructed such that rotation of the displacer around the eccentricselectively draws liquid into the displacer through the outlet openingfrom the eccentric leading into the displacer when the radial spacebetween the annular surface and the peripheral surface of the eccentricis increasing and dispenses liquid from the displacer through the inletopening to the other opening downstream when the radial space betweenthe annular surface and the peripheral surface of the eccentric isdecreasing.
 4. The pump of claim 3, wherein at least one of the outletopening and the inlet opening includes a non-return valve permittingflow in only one direction, such that the outlet opening will permitflow outward through the peripheral surface and the inlet opening willpermit flow inward through the peripheral surface.
 5. The pump of claim1, further comprising an electric motor in the housing, the hollow shaftcomprises a rotor of the motor, and the hollow shaft having armaturewindings thereon to serve as the motor rotor.
 6. The pump of claim 1,further comprising a section of the housing located outward of the shaftand serving as the medium supply to the displacer.
 7. The pump of claim1, wherein the displacer is freely rotatable with respect to theeccentric.
 8. The pump of claim 1, wherein the displacer comprisesafirst dispenser element which travels over the eccentric to be movedradially with respect to the annular surface as the first displacerelement rotates around the eccentric; and a second displacer elementcircumferentially and axially at the first displacer element, andresting against the annular surface and radially movable with referenceto the first displacer element as they rotate around the eccentric; thefirst and second displacer elements being shaped for defining a chamberwithin the displacer which increases an internal volume as the seconddisplacer element moves radially outward and decreases in internalvolume as the second displacer element moves radially inward.
 9. Thepump of claim 8, wherein the displacer includes a sealing element whichrests sealingly against the eccentric and cooperates with the firstdisplacer element.
 10. The pump of claim 9, wherein the sealing elementcomprises a sealing shoe around the eccentric which is concavely shapedto the eccentric.
 11. The pump of claim 9, further comprising a valvering around the eccentric, bores through the valve ring communicatingfrom the eccentric into the displacer for enabling the mixture to passbetween the eccentric and the displacer, the sealing element of thedisplacer resting upon the valve ring and being rotatable with the valvering.
 12. The pump of claim 11, wherein the first displacer element isheld in the radial direction on the valve ring.
 13. The pump of claim11, further comprising a groove defined in one of the first displacerelement and the valve ring at the first displacer element, and a luginsertable into the groove located on the other of the first displacerelement and the valve ring at the first displacer element, such thatengagement between the lug and the groove holds the first displacerelement in the radial direction of the valve ring.
 14. The pump of claim11, further comprising a groove defined in the first displacer elementand a lug defined on the valve ring and the lug engaging in the groovefor holding the first displacer element in the radial direction of thevalve ring.
 15. The pump of claim 8, further comprising a spring betweenthe first and second displacer elements normally urging the seconddisplacer element against the annular surface.
 16. The pump of claim 1,wherein there are a plurality of the displacers arrayed around theeccentric.
 17. The pump of claim 16, wherein the plurality of displacersare arranged in one transverse plane through the eccentric.
 18. The pumpof claim 1, further comprising a cover sealing off the housing andconnected to the eccentric.
 19. The pump of claim 1, further comprisinga plurality of the displacers on the eccentric array in several planestransverse to the axis of the eccentric.
 20. The pump of claim 19,wherein the eccentric includes a plurality of eccentric sectionstherealong having different eccentricities relative to the axis of theannular surface and each of the different eccentricities being at arespective one of the plurality of the spacers at a respective plane.